1. Field of the Invention
The present invention relates to an electron anti-reflection arrangement and, more particularly, to an anti-reflection arrangement for use in electron-beam lithography to improve electron-beam lithography precision.
2. Description of Related Art
When incident electrons penetrate an electron resistant layer to collide with substrate atoms, a number of incident electrons return to the substrate surface through a relatively great angle of scattering, thereby causing the electron resistant layer around the exposed area to receive an extra exposure dosage that affects the profile and depth of the surrounding exposure pattern. This phenomenon is called the electron beam proximity effect.
In detail, as shown in FIG. 1, when an incident electron beam 1 strikes the electron resistant layer 3, a number of incident electrons collide with atoms of the electron resistant layer 3. Because the arrangement of the electron resistant layer is sparse and the atomic spacing of the electron resistant layer is broad, a number of incident electrons fall at a relatively small forward scattering angle xcex8f, thereby causing the diameter of the incident electron beam 1 to be increased after passing through the electron resistant layer. When the incident electron beam 1 passes the electron resistant layer 3 to the substrate 4, a number of incident electrons fall at a relatively greater backward scattering angle xcex8b due to relatively smaller atomic spacing of the substrate 4, and a number of incident electrons may return to the electron resistant layer 3. As illustrated in FIG. 1, the incident electron beam 1 originally has an incident diameter d; however the diameter of the reflected electron beam 2 becomes D after forward scattering and backward scattering, which is much greater than the incident diameter d. This condition directly affects the dimensions of the pattern of the surrounding exposure. Due to different electron beam proximity effects, it is difficult to control the accuracy of pattern dimensions.
When proceeding with photo mask fabrication by an E-beam writer according to conventional methods, increasing the electron beam accelerating voltage and changing the exposure resistant layers and substrate material so as to reduce the formation of backward scattering electrons and lower the effect of backward scattering electrons is a priority. There are known conventional methods using an E-beam recorder to fabricate compact disk molds. These methods are used to improve the electron beam proximity effect by increasing the electron beam accelerating voltage. However, since such accelerating voltage must be as high as 100 KV, much higher than the accelerating voltage a regular 30xcx9c40 KV electron gun can provide, it results in high abeam recorder costs. Therefore, these methods are still not perfect. Further, increasing the electron beam accelerating voltage to 100 KV will lower the sensitivity of the electron resistant layer to electrons, resulting in low E-beam recorder productivity levels.
Therefore, it is desirable to provide an electron anti-reflection arrangement that improves the electron beam proximity effect.
The present invention has been accomplished under the circumstances in view.
The main object of the present invention is to provide an electron anti-reflection arrangement that improves the problems resulting from electron beam proximity effects during electron beam lithography.
Another object of the present invention is to provide an electron anti-reflection arrangement that improves the problem of electron beam proximity effects, and greatly reduces equipment cost and increases productivity.
To achieve these and other objects of the present invention, the electron anti-reflection arrangement comprises a substrate, an electron resistant layer formed on a top side of the substrate, and at least one electron anti-reflective layer provided in between the substrate and the electron resistant layer. Each said at least one anti-reflective layer comprises a composition having an atomic number smaller than that of said substrate, and atoms in said at least one anti-reflective layer have an arrangement sparser than that of atoms in said substrate, i.e., atoms in said at least one anti-reflective layer have an atomic spacing greater than that of said substrate so that the amount of backward scattering ofelectrons is minimized when the electron beam strikes the substrate.
Further, in the electron anti-reflective layer, the atomic spacing in the incident direction of the electron beam is greater than that in the reflective direction, i.e., at least one anti-reflective layer is directional so that the arrangement of atoms in the electron beam incident direction is sparser to facilitate the incidence of the electron beam; the arrangement of atoms in the oblique reflective direction is relatively denser to impede the return of reflected electrons to the electron resistant layer.
Each electron anti-reflective layer can be formed on the substrate by deposition coating, for example, sputtering deposition, evaporation deposition, or any other equivalent deposition method. In one embodiment of the present invention, two anti-reflective layers are provided wherein the first anti-reflective layer is composed of carbon or aluminum while neighboring the substrate; the second anti-reflective layer is composed of silicon dioxide or silicon nitride while neighboring the electron resistant layer.